Description
The test procedures in this section are based on the assumption there is a DTC or problem with the component being tested.
Do checks in sequence unless directed otherwise. If a test point is out of specification, the comment area will direct the technician to the possible cause or to another test point. It is not necessary to complete all the test points, unless additional assistance is needed to Pin-point the fault.
Pin-grip Inspection
Figure 120 Pin grip check
1. Disconnect the harness connector from the sensor or actuator.
2. Inspect for corrosion, bent pins, spread pins, or conditions that could cause a loose or intermittent connection.
3. Check the pin grip in the female pin by inserting the correct tool from Terminal Test Kit.
Diagnostics with EST
Sensors can be diagnosed quickly using an Electronic Service Tool (EST) with ServiceMaxx™ software. The tool monitors sensor signals back to the ECM while testing the sensor’s harness connection. Start this procedure with Sensor End Diagnostics.
Actuators can be diagnosed using ServiceMaxx™
software to command Output State test (high or low) while measuring voltage at the actuator’s harness connection.
Diagnostics without EST
Sensors can also be diagnosed using only a Digital Multimeter (DMM). Start this test procedure with Pin-point Diagnostics.
Sensor End Diagnostics (with ServiceMaxx™
software)
Sensor End Diagnostics (2-Wire)
1. Connect the EST to the Diagnostic Connector.
2. Turn ignition switch ON, engine OFF.
3. Start ServiceMaxx™ software.
4. Open the Continuous Monitor session. This session lists all engine sensors.
Figure 121 Sensor voltage
5. Monitor the sensor voltage and verify an active DTC is present.
NOTE: If sensor signal circuit is shorted or open, the signal value will read NA or Error.
• If the code is inactive, monitor the signal while wiggling the connector and all wires at suspected locations.
If the circuit is interrupted, the signal will spike.
Isolate the fault and repair.
• If the code is active, continue to the next step.
6. Disconnect sensor. Inspect the connector for damaged pins. Repair as necessary.
Example
Connect breakout harness, leave sensor disconnected. Verify specified DTC goes active when fault is induced.
Test Point Spec Comment
EST – Check DTC SPN 175
FMI 3
If SPN 175 FMI 4 is active, check EOT signal for short to GND. Do Harness Resistance Check.
• If specified DTC does not go active, repair short to Ground (GND) on the sensor signal circuit.
Do Harness Resistance Check if additional assistance is needed in diagnosing fault.
• If specified DTC goes active, continue to next test point.
7. Short 3-Banana Plug Harness across the sensor signal circuit and engine GND.
8. The specified DTC should go active, unless the sensor signal circuit is open.
Example
Test Point Spec Comment
EST – Check DTC
Short 3-Banana Plug Harness across 2 and GND
SPN 175 FMI 4
If SPN 175 FMI 3 is active, check EOT signal circuit for OPEN. Do Harness Resistance Check.
• If specified DTC does not go active, repair open in sensor signal circuit. Do Harness Resistance Check if additional assistance is needed in diagnosing fault.
• If specified DTC goes active, continue to next test point.
9. Short 3-Banana Plug Harness across the sensor signal circuit and Signal Ground (SIG GND) circuit.
10. The specified DTC should go active, unless the SIG GND circuit is open.
Example
Test Point Spec Comment
EST – Check DTC
Short 3-Banana Plug Harness across 1 and 2
SPN 175 FMI 3
If DTC is not active, check SIG GND for OPEN. Do Harness Resistance Check.
• If corresponding DTC does not go active, repair open in SIG GND circuit. Do Harness Resistance Check if additional assistance is needed in diagnosing fault.
• If within specification, and both circuits tested acceptable, continue to the last step.
11. Connect the sensor and clear the DTC’s, start the engine, and cycle the accelerator pedal a few times. If the active code remains, the sensor must be at fault. Replace the failed sensor.
Example
If checks are within specification, connect sensor and clear DTCs. If active code remains, replace sensor.
Sensor End Diagnostics (3-Wire)
1. Connect the EST to the Diagnostic Connector.
2. Turn ignition switch ON, engine OFF.
3. Start ServiceMaxx™ software.
4. Run Continuous Monitor session. (This session lists all engine sensors.)
5. Monitor the sensor voltage and verify that an active DTC is present.
NOTE: If sensor signal circuit is shorted or open, the signal value will read NA or Error.
• If the code is inactive, monitor the signal while wiggling the connector and all wires at suspected locations.
If the circuit is interrupted, the signal will spike.
Isolate the fault and repair.
• If the code is active, continue to the next step.
6. Disconnect the sensor. Inspect the connector for damaged pins. Repair as necessary.
Example
Test Point Spec Comment
EST – Check DTC SPN 102
FMI 4
If SPN 102 FMI 3 is active, check IMP signal for short to Power (PWR)
• If specified DTC does not go active, repair short to voltage on sensor signal circuit.
• If specified DTC goes active, continue to next test point.
7. Use a DMM to measure voltage on the Reference Voltage (VREF) circuit. Voltage should read 5 volts, unless VREF is open or shorted to GND, or a voltage is greater than VREF.
Example
Test Point Spec Comment
DMM – Measure volts 2 to GND
5 V If > 5.5 V, check VREF for short to PWR.
If < 4.5 V, check VREF for OPEN or short to GND. Do Harness Resistance Check.
• If not within specification, repair open or short in VREF circuit. Do Harness Resistance Check if additional assistance is needed in diagnosing fault.
• If within specification, continue to the next test point.
8. Short 3-Banana Plug Harness across VREF and the sensor signal circuit.
9. The specified DTC should go active, unless the sensor signal circuit is open.
Example
Test Point Spec Comment
EST – Check DTC
Short breakout harness across 2 and 3
SPN 102 FMI 3
If SPN 102 FMI 4 is active, check IMP signal for OPEN or short to GND. Do Harness Resistance Check.
• If specified DTC does not go active, repair open in sensor signal circuit. Do Harness Resistance Check if additional assistance is needed in diagnosing fault.
• If specified DTC goes active, continue to the next test point.
10. Use a DMM to measure resistance on the SIG GND circuit to ground. Resistance should read less than 5 ohm, unless the SIG GND is open.
Example
Test Point Spec Comment
DMM – Measure resistance 1 to GND
< 5 Ω If > 5 Ω, check SIG GND for OPEN. Do Harness Resistance Check.
• If not within specification, repair open in the SIG GND circuit. Do Harness Resistance Check if additional assistance is needed in diagnosing fault.
• If within specification, and all three circuits tested acceptable, continue to the last step.
11. Connect the sensor and clear the DTC’s. If the active code remains, the sensor must be at fault.
Replace the failed sensor.
Example
If checks are within specification, connect sensor and clear DTCs. If active code remains, replace sensor.
Pin-point Diagnostics (without ServiceMaxx™
software)
1. Connect breakout harness to the engine harness.
Leave sensor disconnected.
2. Turn ignition switch ON, engine OFF.
3. Use a DMM to measure voltage on each circuit to engine ground.
Example
Test Point Spec Comment
C to GND 5 V If > 5.5 V, check VREF for short to PWR.
If < 4.5 V, check VREF for OPEN or short to GND. Do Harness Resistance Check.
• If the circuit is not within specification, the comment area will list possible cause or direct the technician to the next test point.
Do Harness Resistance Check if additional assistance is needed in diagnosing fault.
• If the circuit is within specification, continue to the next test point.
Actuator Operational Voltage Check – Output State Test
This test will allow the technician to take voltage measurements on actuators commanded high or low.
1. Disconnect actuator. Inspect connector for damaged pins. Repair as necessary.
2. Connect breakout harness between engine harness and actuator.
3. Connect the EST to the Diagnostic Connector.
4. Turn ignition switch ON, engine OFF.
5. Start ServiceMaxx™software.
6. Open the Output State session. This session allows the technician to monitor the state of all engine actuators.
7. Run the Output State test (high or low) or Glow Plug / IAH test.
8. Use a DMM to measure voltage on each circuit to engine ground.
Example
Test Point Test Spec Comment
A to GND Key ON-Engine OFF (KOEO)
B+ If < B+, check for OPEN circuit.
B to GND Key ON-Engine OFF (KOEO)
B+ If < B+, check actuator coil for OPEN.
B to GND Output State HIGH B+ If < B+, check actuator control circuit for short to GND.
B to GND Output State LOW 7.5 V If > 7.5 V, check actuator control circuit for OPEN or short to PWR or failed across coil.
• If any circuit is not within specification, the comment area will list possible cause or direct the technician to the next test point.
• If all circuits are within specification, the actuator may not be operating mechanically.
Harness Resistance Check
Complete Sensor End Diagnostics or Pin-point Diagnostics tests before using this procedure.
Resistance cannot be measured on a circuit if voltage is present. Isolate circuit from voltage before continuing.
1. Turn ignition switch to OFF or disconnect batteries.
WARNING: To prevent personal injury or death, always disconnect main negative battery cable first. Always connect the main negative battery cable last.
2. Connect breakout box and breakout harness to vehicle or engine harness. Leave ECM and sensor or actuator disconnected.
3. Use a DMM to measure resistance on each circuit from point to point, then to engine ground.
Example
Test Point Spec Comment
Operational Voltage Check
This test shows what a normal sensor or actuator should read at certain operating conditions. This test is helpful in diagnosing in-range faults or intermittent problems.
1. Connect breakout box or breakout harness between ECM and the component being tested.
2. Turn ignition switch to ON.
3. Open Continuous Monitor session or Output State test session (dependent upon what is being tested) using the ServiceMaxx™ software.
4. Run the Continuous Monitor test.
5. Verify actual sensor or actuator readings are within specification.
Example
Test Point Condition DMM Signal Value
Foot off pedal 0.64 V ± 0.5 V 0%
APP
A to GND or C-48 to GND
Pedal to floor 3.85 V ± 0.5 V 102%
Foot off pedal 0 V 0 V
APP2
D to GND or C-33 to GND
Pedal to floor B+ B+